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<h1 align="center">Libvir the virtualization API</h1>

<h1>Note: this is the flat content of the <a href="index.html">web
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<h1 style="text-align: center">libvir</h1>

<p>Libvir is a C toolkit to interract with the virtualization capabilities of
recent versions of Linux (and other OSes). It is free software available
under the <a href="http://www.opensource.org/licenses/lgpl-license.html">GNU
Lesser General Public License</a>. Virtualization of the Linux Operating
System means the ability to run multiple instances of Operating Systems
concurently on a single hardware system where the basic resources are driven
by a Linux instance. The library aim at providing long term stable C API
primarily for the <a
href="http://www.cl.cam.ac.uk/Research/SRG/netos/xen/index.html">Xen
paravirtualization</a> mechanism but should be able to integrate other
virtualization mechanisms if needed.</p>

<h2><a name="News">Releases</a></h2>

<p>There is no official release yet, just CVS state and snapshot, contact the
mailing list and check the <a href="ChangeLog.html">ChangeLog</a> to gauge
progresses.</p>
<ul>
  <li>Extending the API</li>
</ul>

<h3>0.0.1: Dec 19 2005</h3>
<ul>
  <li>First release</li>
  <li>Basic management of existing Xen domains</li>
  <li>Minimal autogenerated Python bindings</li>
</ul>

<h2><a name="Introducti">Introduction</a></h2>

<p></p>

<h2><a name="architecture">libvir architecture</a></h2>

<p>In a Xen environment, programs using libvir have to execute in "Domain 0",
which is the primary Linux OS loaded on the machine. That OS kernel provides
most if not all of the actual drivers used by the set of domains. It also
runs the Xen Store, a database of informations shared by the hypervisor, the
kernels, the drivers and the xen daemon. Xend, the xen daemon, also runs in
Domain0 and supervise the control and execution of the sets of domains. The
hypervisor, drivers, kernels and daemons communicate though a shared system
bus implemented in the hypervisor. The figure below tries to provide a view
of this environment: </p>
<img src="architecture.gif" alt="The Xen architecture">

<p>The library can be initialized in 2 ways depending on the level of
priviledge of the embedding program. If it runs with root access,
virConnectOpen() can be used, it will use a read/write connection to the Xen
Store and use Xen Hypervisor calls when possible. If it runs without root
access virConnectOpenReadOnly() should be used, it will try to open the
read-only socket <code>/var/run/xenstored/socket_ro</code> to connect to the
Xen Store. In this case use of hypervisor calls and write to the Xen Store
will not be possible, restraining the amount of APIs available and slowing
down information gathering about domains. We expect libvir will also conmnect
to the Xend daemon for some of the domain control operations, though this is
not the case in the 0.0.1 initial version.</p>

<h2><a name="Downloads">Downloads</a></h2>

<p>The latest versions of libvir can be found on the  <a
href="ftp://libvir.org/libvir/">libvir.org</a> server ( <a
href="http://libvir.org/sources/">HTTP</a>, <a
href="ftp://libvir.org/libvir/">FTP</a>). You will find there the released
versions as well as <a
href="http://libvir.org/sources/libvir-cvs-snapshot.tar.gz">snapshot
tarballs</a> updated from CVS head every hour</p>

<p>Anonymous <a href="http://ximbiot.com/cvs/cvshome/docs/">CVS</a> is also
available, first register onto the server:</p>

<p><code>cvs -d :pserver:anoncvs@libvir.org:2401/data/cvs login</code></p>

<p>it will request a password, enter <strong>anoncvs</strong>. Then you can
checkout the development tree with:</p>

<p><code>cvs -d :pserver:anoncvs@libvir.org:2401/data/cvs co libvir</code></p>

<p>Use ./autogen.sh to configure the local checkout, then <code>make</code>
and <code>make install</code>, as usual. All normal cvs commands are now
available except commiting to the base.</p>

<h2><a name="FAQ">FAQ</a></h2>

<p>Table of Contents:</p>
<ul>
  <li><a href="FAQ.html#License">License(s)</a></li>
  <li><a href="FAQ.html#Installati">Installation</a></li>
  <li><a href="FAQ.html#Compilatio">Compilation</a></li>
  <li><a href="FAQ.html#Developer">Developer corner</a></li>
</ul>

<h3><a name="License">License</a>(s)</h3>
<ol>
  <li><em>Licensing Terms for libvir</em>
    <p>libvir is released under the <a
    href="http://www.opensource.org/licenses/lgpl-license.html">GNU Lesser
    General Public License</a>, see the file COPYING.LIB in the distribution
    for the precise wording. The only library that libvir depends upon is the
    Xen store access library which is also licenced under the LGPL.</p>
  </li>
  <li><em>Can I embed libvir in a proprietary application ?</em>
    <p>Yes. The LGPL allows you to embed libvir into a proprietary
    application. It would be graceful to send-back bug fixes and improvements
    as patches for possible incorporation in the main development tree. It
    will decrease your maintainance costs anyway if you do so.</p>
  </li>
</ol>

<h3><a name="Installati">Installation</a></h3>
<ol>
  <li><em>Where can I get libvir</em> ?
    <p>The original distribution comes from <a
    href="ftp://libvir.org/libvir/">ftp://libvir.org/libvir/</a>.</p>
  </li>
  <li><em>I can't install the libvir/libvir-devel RPM packages due to failed
    dependencies</em>
    <p>The most generic solution is to re-fetch the latest src.rpm , and
    rebuild it locally with</p>
    <p><code>rpm --rebuild libvir-xxx.src.rpm</code>.</p>
    <p>If everything goes well it will generate two binary rpm packages (one
    providing the shared libs and virsh, and the other one, the -devel
    package, providing includes, static libraries and scripts needed to build
    applications with libvir that you can install locally.</p>
    <p>One can also rebuild the RPMs from a tarball:</p>
    <p><code>rpmbuild -ta libdir-xxx.tar.gz</code></p>
    <p>Or from a configured tree with:</p>
    <p><code>make rpm</code></p>
  </li>
  <li><em>Failure to use the API for non-root users</em>
    <p>Large parts of the API are only accessible as root, however the read
    only access to the xenstore data doesnot have to be forbidden to user, at
    least for monitoring purposes. If "virsh info" fails to run as an user,
    change the mode of the xenstore read-only socket with:</p>
    <p><code>chmod 666 /var/run/xenstored/socket_ro</code></p>
  </li>
</ol>

<h3><a name="Compilatio">Compilation</a></h3>
<ol>
  <li><em>What is the process to compile libvir ?</em>
    <p>As most UNIX libraries libvir follows the "standard":</p>
    <p><code>gunzip -c libvir-xxx.tar.gz | tar xvf -</code></p>
    <p><code>cd libvir-xxxx</code></p>
    <p><code>./configure --help</code></p>
    <p>to see the options, then the compilation/installation proper</p>
    <p><code>./configure [possible options]</code></p>
    <p><code>make</code></p>
    <p><code>make install</code></p>
    <p>At that point you may have to rerun ldconfig or a similar utility to
    update your list of installed shared libs.</p>
  </li>
  <li><em>What other libraries are needed to compile/install libvir ?</em>
    <p>Libvir requires libxenstore, which is usually provided by the xen
    packages as well as the public headers to compile against libxenstore.</p>
  </li>
  <li><em>I use the CVS version and there is no configure script</em>
    <p>The configure script (and other Makefiles) are generated. Use the
    autogen.sh script to regenerate the configure script and Makefiles,
    like:</p>
    <p><code>./autogen.sh --prefix=/usr --disable-shared</code></p>
  </li>
</ol>

<h3><a name="Developer">Developer</a> corner</h3>
<ol>
  <li><em>Troubles compiling or linking programs using libvir</em>
    <p>To simplify the process of reusing the library, libvir comes with
    pkgconfig support, which can be used directly from autoconf support or
    via the pkg-config command line tool, like:</p>
    <p><code>pkg-config libvir --libs</code></p>
  </li>
</ol>

<h2><a name="Reporting">Reporting bugs and getting help</a></h2>

<p>There is a mailing-list <a
href="mailto:libvir-list@redhat.com">libvir-list@redhat.com</a> for libvir,
with an  <a href="https://www.redhat.com/archives/libvir-list/">on-line
archive</a>. Please subscribe to this list before posting by visiting the <a
href="https://www.redhat.com/mailman/listinfo/libvir-list">associated Web</a>
page and follow the instructions. Patches with explanations and provided as
attachments are really appreciated and will be discussed on the mailing list.
If possible generate the patches by using cvs diff -u in a CVS checkout.</p>

<p>We expect to use <a href="https://bugzilla.redhat.com/">Red Hat
Bugzilla</a> to track bugs for libvir, though there isn't yet a libvir
software module.</p>
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